The Olympic track star began his personal defence of the murder charge on Monday by tearfully apologising to the family and friends of model and law graduate, Reeva Steenkamp.

But he also spoke of how he too has suffered, telling the court he is plagued by graphic nightmares about what took place in his home in the early hours of Valentine’s Day last year, as well as being medicated for depression and insomnia.

“I’m scared to sleep,” he told the court as he fought back tears.

“I have terrible nightmares about things that happened that night, where I wake up and I can smell blood, and I wake up to being terrified. I wake up just in a complete state of terror to a point that I’d rather not sleep than fall asleep and wake up like that.”

In the most eagerly anticipated day of the trial so far, the Olympian began his evidence with an emotional public apology to the Steenkamp family, in particular Reeva’s mother June, who sat in the public gallery of the Pretoria High Court.

“I’d like to take this opportunity to apologise to Reeva's family, and those of you who knew her that are here today,” he said, fighting back tears.

“I would like to apologise and say there hasn't been a moment since this tragedy happened that I haven’t thought about her family ... I wake up every morning and you’re the first people I think of, the first people I pray for.”

Appearing to address June Steenkamp directly, he looked toward her as he said he cannot imagine the “pain, sorrow and the emptiness that I have caused you and your family.”

“I can promise that when she went to bed that night she felt loved.”

It was the first time Pistorius had directly apologised for his actions – intentional or not – and he immediately sought to quell any criticism that it was 14 months too late.

“I’ve tried to put my words on paper many, many times to write to you, but no words would ever suffice,” he said.

Mrs Steenkamp stared straight ahead as Pistorius spoke.

In carefully orchestrated testimony, the man dubbed the Blade Runner because of his extraordinary speed on prosthetic legs told the court about his double-amputation shortly after birth, his close-knit family, his late mother who encouraged him to see his disability was no disadvantage, his charity work, and his firm religious faith.

It was a markedly different side of the athlete, who the state painted as a gun-loving, trigger-happy, arrogant and reckless young man.

Pistorius smiled but then blinked back tears as he spoke about his beloved late mother Sheila, who died when he was 15.

Having been born without either fibula, he had both legs amputated below the knee before he was two years old, but said his mother “made me feel equal to the rest of the kids.”

“She didn't see my disability as something that should hold me back,” he said.

As his siblings Aimee and Carl watched on, also in tears, he added: “Everything we learnt in life, we learnt from her.”

Pistorius’ legal team wants Judge Thokozile Masipa to believe Pistorius was a man so fearful of violent attacks that he was indeed capable of shooting an intruder through the toilet door of his home, as he maintains.

In that vein, Pistorius described being aware of crime as far back as his childhood.

“Everyone in South Africa has been exposed to crime at some point,” he said.

“My mother, she had a pistol. She often would get scared at night and she would phone the police,” he said. “She kept her firearm in a padded bag under her pillow.”

He said even on the day leading up to the fatal shooting of Ms Steenkamp, he had tried to discourage a cousin from driving to Pretoria in his new VW Golf because it would leave him open to car-jacking.

While the court has previously heard from police that Pistorius has never reported to them being a victim of crime, he nonetheless detailed several incidents in which he claims to have been shot at, followed home and burgled, among other things.

The defence is also trying to establish that Pistorius felt defenceless without his prosthetic legs, which he was the night he shot and killed Ms Steenkamp.

The double-amputee told the court he had limited mobility and balance without them, adding that his dog could knock him over if he wasn’t wearing his false limbs.

Saying he often felt “embarrassed” or “shy” about his legs, Pistorius told the court he had been in talks with a surgeon to “redo” his left stump, as it is one centimetre shorter than the right.

As his barrister Barry Roux SC led the athlete through his evidence-in-chief over two hours, he revealed that when his lower legs were amputated, his heel pads were reattached to the stumps - but he now needs to have the left one corrected as it has rotated behind the end of the limb.

Mr Roux asked what he does with his prosthetic limbs when he is not wearing them.

“I keep them close by me, I usually let them air at night,” he said, adding he will often leave his trousers on them, so that they can be easily put back on.

Mr Roux told the court he would call between 14 and 17 witnesses.

Earlier, Pistorius once again appeared to heave and retch in the dock as his legal team’s first witness, pathologist Professor Jan Botha, described Ms Steenkamp’s injuries as part of his testimony – and her bloodied skull was again flashed up on the screens in court.

The athlete was also able to glimpse the cross-examination style of chief prosecutor Gerrie Nel who aggressively questioned Prof Botha, securing at least two key concessions.

Pistorius denies intentionally killing Ms Steenkamp, saying he shot her believing she was an intruder.

He also told the court he has not picked up a gun since the incident, and never wanted to again.

The case, and the Blade Runner’s evidence-in-chief, continues on Tuesday morning.